: The proposal hopes to determine whether the expression of stress genes play an important role in cell survival following cerebral ischemia. The proposal will focus on the expression of HSP-70 mRNA, which codes for the major inducible 70 kilodalton heat shock protein. In situ hybridization will be used to detect the expression of HSP-70 mRNA following ischemia. A reversible model of focal ischemia in rat brain will be employed. This produces cortical infarction in the territory of the middle cerebral artery. The specific aims are to: (1) determine the timecourse and regional expression of HSP-70 mRNA following focal ischemia in rat brain using in situ hybridization, and correlate this expression with the regional extent of histological injury; (2) to determine whether prior induction of HSP-70 protects brain tissue against a subsequent period of ischemia; (3) to determine whether a known protectant, hypothermia, alters the expression of HSP-70 following focal ischemia; (4) to determine whether ischemia enhances the expression of other stress-related genes (c-fox, HSP-90, ubiquitin, glucose-regulated protein, ornithine decarboxylase), using in situ hybridization and (5) to determine whether enhanced expression of HSP-70 mRNA is triggered by a decrease in high-energy phosphates and/or an increase in lactate during the ischemic insult.